Daily Archives: September 18, 2018

Science

Jupiter Has Two Magnetic South Poles

Jupiter as seen from the Juno spacecraft.
NASA/JPL-Caltech/SwRI/MSSS/Gabriel Fiset

A complex dynamo inferred from the hemispheric dichotomy of Jupiter’s magnetic field

The Juno spacecraft, which is in a polar orbit around Jupiter, is providing direct measurements of the planet’s magnetic field close to its surface. A recent analysis of observations of Jupiter’s magnetic field from eight (of the first nine) Juno orbits has provided a spherical-harmonic reference model (JRM09) of Jupiter’s magnetic field outside the planet.

The non-dipolar nature of the magnetic field in the northern hemisphere and the dipolar nature in the southern hemisphere is apparent. The equatorial view is centred near the Great Blue Spot and shows the linkage of magnetic field lines that enter through the Great Blue Spot. The contoured surface on which the field lines shown start and end is at r = 0.85RJ, where the density of field lines is proportional to the radial magnetic field strength and is depicted by the colour scale (red outward flux, blue inward flux).

This model is of particular interest for understanding processes in Jupiter’s magnetosphere, but to study the field within the planet and thus the dynamo mechanism that is responsible for generating Jupiter’s main magnetic field, alternative models are preferred.

The authors report maps of the magnetic field at a range of depths within Jupiter. They find that Jupiter’s magnetic field is different from all other known planetary magnetic fields. Within Jupiter, most of the flux emerges from the dynamo region in a narrow band in the northern hemisphere, some of which returns through an intense, isolated flux patch near the equator. Elsewhere, the field is much weaker. The non-dipolar part of the field is confined almost entirely to the northern hemisphere, so there the field is strongly non-dipolar and in the southern hemisphere it is predominantly dipolar. The authors that Jupiter’s dynamo, unlike Earth’s, does not operate in a thick, homogeneous shell, and we propose that this unexpected field morphology arises from radial variations, possibly including layering, in density or electrical conductivity, or both.

Original Research

Full Text

Geoscience

Geological Belts, Plate Boundaries, and Mineral Deposits in Myanmar

Geological Belts, Plate Boundaries and Mineral Deposits in Myanmar

 

Just received the above titled book from Elsevier for review.  I had the great pleasure of spending some time in the field in Myanmar with Andrew Mitchell in 2017 and this important contribution by him is a remarkable testament to  his life’s work.  He has enormous knowledge of the geology and mineral deposits of Myanmar and that is obvious in this text.

I will be undertaking a chapter-by-chapter review of the text over the coming 6 weeks or so and posting here.  A quick review:  The text is well written, beautifully presented and the numerous maps provide new geological insights.  As a largely personal contribution this is an unusual work and will be important to minerals industry professionals and researchers and importantly, geoscience educators in Myanmar.

Geological Belts, Plate Boundaries, and Mineral Deposits in Myanmar, Mitchell, A., Elsevier, pp 524, ISBN 978-0-12-803382-1 , https://doi.org/10.1016/C2014-0-00978-1, 2018

Description

Geological Belts, Plate Boundaries and Mineral Deposits in Myanmar arms readers with a comprehensive overview of the geography, geology, mineral potential and tectonic plate activity of Myanmar. The book focuses on the nature and history of the structural belts and terranes of Myanmar, with particular emphasis on the mineral deposits and their relationship to stratigraphy and structure. The country has a long history of plate tectonic activity, and the most recent plate movements relate to the northward movement of the India plate as it collides with Asia. Both of these are responsible for the earthquakes which frequently occur, making the country a geologically dynamic region. Additionally, Myanmar is rich in mineral and petroleum potential and the site of some of Southeast Asia’s largest faults. However, many geoscientists are only recently becoming familiar with Myanmar due to previous political issues. Some of these barriers have been removed and there is emerging international interest in the geology and mineral deposits of Myanmar. This book collates this essential information in one complete resource. Geological Belts, Plate Boundaries and Mineral Deposits in Myanmar is an essential reference for economic geologists, mineralogists, petroleum geologists, and seismologists, as well as geoscience instructors and students taking related coursework.